1. Field of the Invention
The present invention relates to a projection lens to be mounted on a projection-type display apparatus, and the projection-type display apparatus. Particularly, the present invention relates to a projection lens appropriate for a small projector apparatus on which a light valve, such as a transmissive liquid crystal panel, a reflective liquid crystal panel and a DMD (digital micromirror device), is mounted, and to the projector apparatus.
2. Description of the Related Art
As projectors rapidly spread, and became widely used in recent years, a demand for small projectors that are light-weight and low-price, and which are conveniently usable and easily settable, increased. To satisfy such a demand, projections lenses for the projectors also need to be small, light-weight and low-price.
When the back focus of a projection lens is reduced, it is possible to reduce the outer diameter of a reduction-side lens in the projection lens. As such a projection lens, lenses disclosed in Japanese Patent No. 4164283 (Patent Document 1) and Japanese Unexamined Patent Publication No. 2005-215310 (Patent Document 2) are known.
In the projection lenses disclosed in Patent Documents 1 and 2, the outer diameters of the reduction-side lenses can be reduced. However, the number of lenses is 10 or 11, which is many, and the total length is too long. Further, in Patent Documents 1 and 2, an increase in the outer diameter of a magnification-side lens is not considered. Therefore, the size of the entire lens system is not sufficiently reduced.